A rising interest in entropy-stabilized oxides in recent years has been driven by their attractive functional properties. Their synthesis usually requires prolonged exposure at high temperature to promote solid-state diffusion without the application of pressure. In this work, we report the synthesis of a high entropy perovskite, Sr((Zr_0.94Y_0.06)_0.2Sn_0.2Ti_0.2Hf_0.2Mn_0.2)O_3−x, in a relatively short time (minutes instead of hours) using a spark plasma sintering (SPS) furnace. Comparative analysis showed that conventional pressureless sintering at 1500°C for 2 h results in porous materials with large thermodynamically stable pores (tens of µm), while SPS processing produces dense materials in a single step by reactive sintering at 1475°C in 9 min. SPS is therefore an attractive route for the production, synthesis and sintering of dense high-entropy oxides.

Guided by the theoretical prediction, a new MAX phase V₂SnC was synthesized experimentally for the first time by reaction of V, Sn, and C mixtures at 1000 °C. The chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and high resolution scanning transmission electron microscopy (HR-STEM). The stacking sequence of V₂C and Sn layers results in a crystal structure of space group P6₃/mmc. The a- and c-lattice parameters, which were determined by the Rietveld analysis of powder XRD pattern, are 0.2981(0) nm and 1.3470(6) nm, respectively. The atomic positions are V at 4f (1/3, 2/3, 0.0776(5)), Sn at 2d (2/3, 1/3, 1/4), and C at 2a (0, 0, 0). A new set of XRD data of V₂SnC was also obtained. Theoretical calculations suggest that this new compound is stable with negative formation energy and formation enthalpy, satisfied Born-Huang criteria of mechanical stability, and positive phonon branches over the Brillouin zone. It also has low shear deformation resistance c₄₄ (second-order elastic constant, c_ij) and shear modulus (G), positive Cauchy pressure, and low Pugh’s ratio (G/B = 0.500 < 0.571), which is regarded as a quasi-ductile MAX phase. The mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.